Various gaseous pollutants have been found present in ground soil. These gaseous pollutants can be naturally occurring, such as radon gas, or can be caused by artificial conditions, such as gases produced during the decay processes associated with land fills and solid waste disposal sites. Such gaseous pollutants can have insidious effects if allowed to concentrate to any extent. For example, naturally occurring radon gas is radioactive and know to be carcinogenic when inhaled by humans. The harmful effects of exposure to radon gas to human health and longevity is equated to smoking an equivalent number of packages of cigarettes per day or exposure to an equivalent number of medical chest x-rays on a daily basis. Using such equivalents, common concentrations of radon gas within homes located in many area of the United States result in heath consequences comparable to smoking two or more packages of cigarettes per day. Further, because of such health consequences, homes and other habitable structures can greatly depreciate in value upon discovery of radon gas contamination.
As indicated, other gaseous contaminates present in the soil can have deleterious effects on the habitability and safety of a structure built in an area subject to gaseous pollutant venting from the soil. In areas of land fills, waste material decomposition processes can generate harmful gaseous waste products. In some situations, these waste products are combustible byproducts of the decomposition processes which pose the danger of explosion if permitted to accumulate in a confined area such as a basement.
If the unimproved land is subject to seepage of such gaseous pollutants, the fumes vent naturally into the atmosphere. However, when land subject to an influx of such gaseous pollutants is improved with a structure, such as a dwelling, the structure is subject to inseepage of the noxious gases.
The presence of such a structure can additionally cause an increase in venting of soil laden gaseous pollutants for several reasons. If the structure includes a basement extending into the surrounding ground, the basement represents a lower resistance path to gaseous transport, resulting in the gaseous pollutants tending to seep into the basement area. Further, in a heated dwelling the thinner warm air results in an area of lower air pressure tending to draw the pollutants from the soil into the dwelling. This effect is further exacerbated due to a chimney effect caused by the tendency of warm air to rise, resulting in further reduction of air pressure within the lower portions of the structure and especially in any basement area. Further, in a dwelling having a fossil fuel type of heating system, the furnace consumes air from within the basement to support combustion. This causes a further decrease in air pressure within the basement, further drawing ground gases into the building.
The gaseous pollutants tend to enter the dwelling through small cracks or gaps in the dwelling foundation which offer lesser resistance to gaseous transport and inseepage from the soil. Such cracks or gaps are often found along the periphery of the foundation and especially in basement areas where the lower end of the basement walls come in contact or abut a foundation floor slab. The gaseous pollutants, entering such basement area along the periphery area tend to rise along the walls and can permeate the upper levels of the structure, travelling inside walls between framing members and further moving upwardly through open spaces such as stair wells or by seeping into and being distributed by the normal dwelling ventilation system.
The problem of such gaseous pollutants concentrating to dangerous levels within confined spaces of dwelling structures has increased as homes are subjected to greater efforts to insulate them to save energy expended for heating and cooling. The stack effect caused by furnace venting combustion air of a fossil fuel furnace can further aggravate the negative pressure problem. Such insulation efforts result in a "tighter" house having less natural ventilation due to air gaps in the structure. This results in higher concentrations of gaseous pollutants once inseepage occurs and is allowed to collect within the dwelling.
To alleviate problems of noxious gaseous pollutants collecting within a dwelling structure, various systems are used to remove the gas including filtration and ventilation systems. In a filtration system, basement air is drawn through a filter which collects airborne particles. Such a filter, for example, can use activated charcoal or ion exchange filtration systems. While these systems can reduce the concentration of radon particles upon entering a dwelling, they fail to extract other gaseous pollutants, such as carbon monoxide caused by furnace operation or noxious gases caused by the decay of organic matter.
Air ventilation systems are used to exchange outside air with air within the dwelling in order to exhaust contaminated air and thereby lower contaminate concentrations to safe levels. Such systems rely on the circulation of air so as to vent the stale polluted air within the building to the outside while venting fresh outside air into the confined space. Some prior ventilation systems utilize passive gaseous transport, essentially comprising one or more basement ventilation openings or windows. Other prior systems comprise active transport using a basement ventilation fan powered by commercial electric power.
Prior system operations, however, can result in the loss of heat energy contained in the building by venting warm air to the outside while venting in cold air, such as would be the case in a cold climate. Alternatively, such a system places additional requirements on cooling systems which may be in use in areas or times of warm weather. Further, such systems are not responsive to the presence of the pollutant so as to adjust system operation, resulting in either inadequate or excessive ventilation and waste of power used both for system operation and building heating and air conditioning.
Another problem of prior noxious gas ventilation systems is that they do not reduce the rate of pollutant influx caused by outgassing from the surrounding soil. In fact, such prior systems often use high air exchange flow rates which can increase the influx rate by further lowering the air pressure within the dwelling, tending to draw the pollutant into the dwelling. Such systems may additionally require difficult installation in a dwelling including requiring modifications to the building structure. Prior systems further fail to address building construction methods for reducing influx of pollutants due to outgassing from the soil.
A need therefore exists to provide an air exchange apparatus for exchanging air inside a cavity with air outside the cavity which reduces heat loss to and heat influx from the outside. Further, a need exists for a system to reduce or inhibit the influx of gaseous pollutants into confined spaces within buildings caused by outgassing from surrounding and underlying soil. Additionally, a need exists for an air exchange apparatus capable of functioning without commercial AC power. A need further exists for a method of dwelling construction which minimizes or inhibits the influx of pollutants due to outgassing from the soil into the dwelling.
Accordingly, an object of the invention is to provide an air exchange apparatus including a heat reclaim exchanger used to recapture building heat.
Another object of the invention is to provide an air exchange apparatus which is not dependent upon commercial AC power to operate but instead uses radiant solar power. A further object of the invention is to provide an air exchange apparatus which reduces or inhibits the influx of gaseous pollutants due to outgassing from surrounding an underlying soil by providing an overpressure within portions of a dwelling to inhibit such influx.
Still a further object of the invention is to control exhausting of gaseous pollutants in response to detecting such pollutants.
Another object of the invention is to provide a method of dwelling construction to collect and exhaust gaseous pollutants prior to seepage into the dwelling and to inhibit gaseous pollutant influx into the dwelling.